As the computer technology advances, particularly the nano technology and chip precision packaging technology are well developed, a single chip usually comes with powerful computation and storage functions, and the single chip becomes very compact, so that a motherboard can install many onboard application specific integrated circuits. Besides simplifying the complicated structure or process of installing display cards, sound cards, network cards, and other special function cards onto a motherboard of a desktop computer, the onboard design also can reduce the size and specification of the motherboard and give a compact and multifunctional computer system. For example, a motherboard usually includes a video chip, an audio chip, and a network chip, or even a central processing unit (CPU) soldered directly onto the motherboard. To meet different customer requirements and make the computer application easy without occupying too much space, the foregoing chips are integrated into a single chip installed onto a motherboard, and the motherboard is installed into a small chassis of a microcomputer system as shown in FIG. 2.
Since the chassis of a microcomputer is very small, the chassis can install a motherboard, a CPU, a memory and necessary disk drives only. The heat dissipation of the CPU and related chips cannot be achieved by the traditional heat dissipating device for desktop computers. In other words, the prior art heat sink that comes with a fan and a relatively tall structure no longer meets the requirements of the heat dissipating device for microcomputer systems. The microcomputer system avoids using additional heat dissipating device that will increase the size of the chassis, and thus an appropriate heat dissipating device is needed for dispersing the heat of the CPU and other related chips to maintain the stability of the operation of the computer system.